'attribute': is incompatible with attribute 'attribute'
Two incompatible attributes were encountered in an attribute block.
The following code sample shows two instances of this error, however, that this error is not limited to the use of custom and dual together, as demonstrated in the attribute block; the error may fire for other incompatible attributes.
#include <unknwn.h> // a COM interface must be either custom or dual, but cannot be both. [ com, uuid("6df06330-5fbd-11d2-97d3-0000f805d73b"), custom, dual ] __interface A { };